summary:
peak pounds force on 8mm axle from torque (75kv, 120a motor): 855.1lbs
pounds force on axle from normal force (200lb vehicle, 4 wheels): 50lbs
assumptions: roughly 75kv 120a motor current, 8mm diameter axle
axle radius: 4mm
torque per amp: 0.127nm/a = 60/(2 * pi * 75kv)
total torque: 15.24nm = 120a * 0.127nm/a
total force at axle: 3817.5 newtons = 15.27nm / 0.004 meters axle radius
total force at axle (pounds force): 855lbs force = 3817.5n * 0.224 pound force per newton
^ the force applied to the axle from torque from the motor was a factor of 17 times greater than the normal force caused by someone standing on the board.